Question

Study the following cases :

Case I : A person bitten by a rabid dog is immediately given an injection of antitoxin for rabies.

Case II : A child is given rabies vaccine as a preventive measure.

(a) Identify the type of immunity provided in both the cases.

(b) Differentiate between the two types of immunity.

(c) What is a vaccine ? How does it help in preventing a disease ?

Hint:

Antitoxin gives passive immunity, a vaccine gives active immunity, and a vaccine works by creating memory cells.

Answer 1

Step 1: (a) Identify the immunity:
Case I: the person gets ready-made antibodies (antitoxin). This is passive immunity.
Case II: the vaccine makes the child's own body form antibodies. This is active immunity.

Step 2: (b) Differences:
Active immunity: the body makes its own antibodies after meeting an antigen. It is slow to start but lasts long, and memory cells are formed.
Passive immunity: ready-made antibodies are given from outside. It acts quickly but lasts only a short time, and no memory cells are formed.

Step 3: (c) Vaccine and its action:
A vaccine is a preparation of weakened or killed pathogens, or their antigenic proteins, given to build immunity.
It causes a primary response and memory B and T cells are formed.
When the real pathogen enters later, the memory cells give a fast and strong secondary response, so the disease is prevented.

Final Answer:
(a) Case I passive, Case II active. (b) Active is self-made and long lasting; passive is ready-made and short. (c) A vaccine primes memory cells against a pathogen.